Method of making corrugated wall tubing



c. T. PAUGH METHOD OF MAKING CORRUGATED WALL TUBING Filed June 16. 1950 ATTORN EYIS Patented May 16, 1933 Umrso sTA'rss PATENT osslca m I. ILUGH, of na'rnorr, IIIIQHIG'AI', ABSIGNOB 'roiwonvmmm ma oonm, OI nrmorr, IIGKIGLI', A CORPORATION 01' IIOHIGA.N

. m6 QRBUGA'IID WALL TUBING" Application 1101! June 10, 1080. Serial Io. 481,500.

This invention relates-to an improvement in finned tubing and method and apparatus for manufacturlng the same. This application has partial reference to copending applications Serial Nos. 237,930 and 322,914.

Heretofore it has been the ractice in this art to make finned tubing with a plain tubular wall, all longitudinal elements of which are substantially parallel to the axis of the tube, either by attaching a fin, or series of fins, to the outside, of a plain tube by various methods, or by rolling integral fins on a seamless tube, by the method and means described in the aforementioned application.

The only variation from a plain surface on the inside of the tube has been whatever slight deformation that may be incidental to the process of manufacture.

In fabricating finned tubing into condens' ers, heaters or other heat transfer units, it-is often desirable or necessary to use bends of comparatively'shortradii. Finned tubing as above described cannot be bent on such a short radius without breaking, except in certain types after stripping oil the fins from the section to be bent. It has therefore been common practice to either sacrifice good features of design to eliminate short bends or to use bends of plain tube, or other connections, brazed or otherwise attached to straight sec-. tions of finned tube.

This invention constitutes an improvement in finned tubing and has as one of its principal objects to provide a finned tube which allows practical bending on short radii without removing fins or making other alterations. A further object of this invention is to produce a tube constructed to increase the turbulence of the fluid passing through the tube; also to increase the internal surface area of the tube, thereby increasing the efficiency of heat transfer.

The invention consists essentially in providing corrugations in the wall of the tube between the fins, and in the method and apparatus for producing the same.

The several objects, advantages and novel details of construction of this invention will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawing, wherein a Figure 1 is aside elevation of ahelically finned 'tube, a portion thereof being shown in longitudinal section and corrugated in ac cordance with the present invention;

Figure 2 is a side elevation ofa helically finned tube partly in longitudinal section and bent on a relatively small radius;

F1 re 3 is a fragmentary longitudinal sectiona elevational view through one form of apparatus employed for forming the fins of the tube shown in Figure 1;

Figure 4 is a transverse sectional view taken substantially on the plane indicated by the line 4-4 in Figure 3;

Figure 5 a sectional elevational view showinga shghtly modified construction of forming roll or roducing corrugations on a tube having a series of longitudinally spaced fins, and v Figure 6 is a fragmentary longitudinal elevational view showing a forming roll for continuous] producing a finned tube having a series 0 longitudinally spaced fins with the wall between the adjacent fins corrugated.

Referring now particularly to Figures 1 to 4 inclusive and particularly to Figures 1 and 2, it will be noted that the problem involved is that of providing corrugations in the wall of the tube between adjacent fins. In Figure 1, the tube is indicated generally by the reference character 10 and is shown as provided with a continuous helical radially extending fin 11 developed from the wall of the tube in the manner and by the means illustrated and described in copending applications, Serial Nos. 237,930 and 322,914 heretofore referred to. In accordance with this invention I propose forming the wall of the tube between adjacent fins with inwardly extending corrugations 12. A seamless tube corrugated in this manner may be bent on short radii as shown in Figure 2 without breaking or otherwise mutilating the fins. As shown in Figure 2 which illustrates a typical section after bending, the corrugations 12' on the outside of the bend have stretched out but the wall thickness has not been reduced. The corrusaid copending application,

gations 12" at the inside of the bend have increased in depth and here also the wall thickness has not been changed. Finned tubing constructed in accordance with this invention may be easily bent on a short radlus without altering t e fins or the strength of the tube.

By reference to Figures 3 and 4,0ne form of apparatus for groducing a finned tube such as illustrated in igures 1 and 2 will be described. As the apparatus for developing the fins from the wall of the tubeis substantially the same as that illustrated in the afore- Serial No. 322,914, and inasmuch as the method of developingthe fins is substantially the same as that described in the aforesaid copending'application, Serial No. 237,930, but brief reference will be made thereto herein. In Figure 3 the tube T is shown as provided with a mandrel 13 arranged therein and providing a. support for the tube during the formation of the fins. The forming mechanism consists of three rolls indicated generally by the reference character 14 (see Figure 4) only one of which is illustrated in Figure 3. These forming rolls are distributed radially around the mandrel 13 over which the tube is fed. Each roll is so fashioned as to first form a V-shape spiral groove in the wall of the tube and to subsequently progressively compress the metal between adjacent grooves axially of the tube so as to reduce the thickness and increase the radial dimensions thereof.

As thus far described, the forming roll structure is the same as described in the aforesaid application but thepresent invention contemplates the addition to each roll of a corrugating or corrugation forming disk 15. This disk 15of each roll is of larger diameter than the remaining portion of the roll and the length of the mandrel 13 is so chosen that the disk operates upon the tube T beyond the end of the mandrel as clearly illustrated in Figure 3. The forming rolls are positively rotated simultaneously at the same peripheral speed and the rotation of the forming rolls causes the tube to be fed through the rolls in the direction of arrow A (see Figure 3).

As previously mentioned, at least three of these forming rolls will be employed, more being employed preferably in connection with tubes of larger diameter. The action of the corrugating disk 15 employed in connection with each forming roll is to radially inwardly deflect the wall of the tube between adjacent fins to form corrugations substantially of the shape and relative size illustrated. The forming rolls are equally spaced around the tube and mounted at the helix angle.

The invention obviously is applicable for use in corrugating helical finned tubes in which the fins have already been formed. Under such conditions the fin forming portion of each roll 14: would be eliminated and three or-more of the corrugating disks 15 would be em loyed so as to corrugate the wall of the tube etween adjacent fins as will be obvious. The rolls would be mounted in the same way but would consist only of the corrugating disks which, however, would be mounte at the helix angle. This corrugating operation mi ht be performed either before or after the ns are produced or attached to the tube and, either with or without a mandrel.

In Figure 5 there is illustrated a mechanism for forming corrugations in a tube having a series of longitudinally spaced fins. In this form of construction the tube T is shown as provided with a plurality of circumferential longitudinally spaced fins 11'. The corrugating mechanism consists of ahelical corrugating disk or member 16 mounted on a shaft 17 While only one of these de- -vices is illustrated in Figure 5, it will be readily understood that three or more of these corrugating devices will be employed equally spaced around the tube as in the previously described construction. The corru ating member 16 engages the wall of the tu beyond the end of the mandrel 13 so as to radially inwardly deflect the wall of the tube to produce the corrugations between adjacent fins as illustrated. Moreover this corrugating operation might be performed either before or after the fins are attached.

In Figure 6 there is illustrated another modified construction of forming roll similar to that illustrated in Figure 3 but designed to produce a series of longitudinally spaced fins similar to the fins shown on the tube illustrated in Fi re 5, but developed from the material of t e wall thereof by the axial compression and radial deflection thereof. While in Figure 6 but one of these forming rolls has been illustrated, three or more will be employed as heretofore. In Figure 6 the forming roll is shown as consisting of a core or body 17 having an abutment 18 at one end thereof and a threaded portion at the other end thereof upon which a nut 19 is secured. Between the abutment 18 and nut 19 a forming roll 20 is clamped, this forming roll having a helically extending profile adapted to first form a V-shape groove in the wall of the tube and to subsequently progressively compress the metal between adjacent grooves axially of the tube so as to reduce the thickness and increase the radial dimension thereof. The profile of the tube adjacent the end thereof terminates in a disk-like projection 21 which engages the wall of the tube beyond the end of the mandrel 13 to radially inwardly deflect the same to produce a corrugation therein as in the previously described construction. Thus with this form of apparatus an integral finned tube may be developed, the fins extending circumferentially of the tube and being longitudinally spaced.

Moreover the wall of the tube between adja-. cent fins is corrugated as in the previously described constructions. Various modifications will suggest themselves to those skilled in this art and to this end reservation is made to make such changes as may come within the purview of the accompanying claims.

What I claim as my invention is:

1. The method of forming corrugated I finned tubing comprising inwardly radially deflecting the interior wall of a finned tube between the fins thereof.

2. The method of producing finned tubing having a'corrugated Wall which consists in rolling the corrugations through the wall of a finned tube between adjacent fins so as to project interiorly of the tube. a I

3. The method of forming finned tubing zohaving corrugated walls which consists in producing a fin on the outer wall of the, tube and subsequently rolling inwardly extending corrugations in the wall of the tube between .adjacent fins, which corrugations extend beyond the interior surface of the tube.

' A. The method of producing finned tub ing having corrugated walls which consists in generating integral fins from the material of the wall of the tube while the tube is sup ported on a mandrel and subsequently rolling radially inwardly extending corru ations in the wall of the tube between the ns beyond the end of the mandrel.

In testimony whereof I atfix my signature. CHARLES T. PAUGH. 

